Monday, May 20, 2013

galvanizing are listed in the following table. The
paint manufacturer can provide more thorough
information about the compatibility of specific
systems with galvanized steel. Always consult
the paint manufacturer prior to painting galvanized
steel. Different physical and chemical characteristics
for the same types of paint may have varied reactions
with a galvanized surface. The paint manufacturer and

galvanizer can assist in the creation of a successful

duplex system.

Type

Compatibility

Comments

Acrylics

Sometimes

If the pH of the paint is high,

problems may occur due to

ammonia reacting with zinc

Aliphatic Polyurethanes

Yes

If used as a top coat for a polyamide epoxy primer, itis considered a superiorduplex system

Alkyds

No

The alkaline zinc surface causes

the alkyds to saponify, causing

premature peeling

Asphalts

No

Petroleum base is usually not

recommended for use ongalvanized steel

Bituminous

Yes

Used for parts that are to beburied in soil

Chlorinated Rubbers

Yes

High VOC content has severely

limited their availability

Coal Tar Epoxies

Sometimes

Rarely used, only if parts are to

be buried in soil

Epoxies

Sometimes

If paint is specifically

manufactured for use with

galvanized steel

Epoxy-Polyamide Cured

Yes

Has superior adherence to

galvanized steel

Latex-Acrylics

Yes

Has the added benefit of being

environmentally friendly

Latex-Water-based

Sometimes

Consult paint manufacturer

Oil Base

Sometimes

Consult paint manufacturer

Portland Cement in Oil

Yes

Has superior adherence to

galvanized steel

Silicones

No

Not for use directly over

galvanized steel, can bebeneficial in high temperaturesystems w/ base coat

and painting or powder coating over hot-dip galvanizing
adds an additional barrier layer on top of the zinc coating,
thus enhancing the protection afforded to the steel. Duplex
coatings also offer the element of color to your project,
making it more aesthetically pleasing.

Fortress Fusion Coatings specializes in duplex coatings,
specifically in powder coating over galvanizing. We
would be happy to discuss your project with you and
answer any questions you may have.

Wednesday, March 13, 2013

Poor adhesion of paint or powder coating to galvanized
parts is a common issue - but it doesn't need to be.
There are a few factors that affect the adhesion between
the surfaces. One of these factors is the post-treatment of

the galvanized steel.

After a piece of steel has been galvanized,
it is sometimes quenched or treated by the
galvanizer, in order to halt the reaction
between the iron and zinc (and to facilitate
immediate shipment of the galvanized steel).

The most common post-treatments are
water quenching and chromate quenching,

Both quenching methods (water and

chromate) can adversely affect the

bond between the galvanized steel

and the paint or powder coating, causing
adhesion issues. Communicating with the
galvanizer prior to galvanizing helps avoid
post-treatments that can be detrimental to
paint or powder adhesion.

At Fortress Fusion Coatings, we are very familiar with the factors affecting proper
adhesion between galvanized steel and paint or powder coating. If you have any
questions about this, or any other coating-related issue, we would be happy to
discuss it with you. Please give us a call:

painting or powder coating, is lower over the entire
life of the product than most single system methods
of corrosion protection.

Ease of Repainting

As the paint film weathers, the zinc in the

galvanized coating is present to provide both

cathodic and barrier protection, until the structure

is repainted. The exposed zinc surface then can

be repainted with minimal surface preparation.

Aesthetics

Galvanizing has an attractive metallic-gray

appearance, suitable for a myriad of applications,

but painting or powder coating can offer aesthetic
advantages. One might choose to paint over a
galvanized coating so that a project matches its
specific environment—such as a stadium, theme
park, or natural habitat.

Safety Marking

A duplex system of galvanized

steel and paint or powder coating
may be used to conform to safety
regulations. For example, the Federal

Aviation Administration (FAA)

requires structures over 200 feet

tall to be painted in the alternating
pattern of white and orange.

Color Coding

Painting or powder coating over galvanized steel
also increases safety in many environments, by
color-coding gas, steam, or chemical pipes,
identifying hazardous work areas and walkways,
and marking high-voltage electrical lines and
equipment.